Increasingly, motor vehicle manufacturers are installing safety devices in motor vehicles to enable drivers to drive in a safer, more efficient manner. For example, some manufacturers have included forward looking systems (FLSs), rear detection systems (RDSs) and side detection systems (SDSs) within certain vehicle models. An adaptive cruise control (ACC) system is one example of an FLS.
A typical ACC system uses a sensor (e.g., a radar or laser sensor), mounted at the front of a host motor vehicle, to detect objects in the forward path of the vehicle. When an object is detected, the ACC system typically compares the projected path of the vehicle to the object location such that objects on the roadside or in different lanes are eliminated. That is, if the lane ahead is clear, the ACC system maintains a set vehicle speed. However, when a slower motor vehicle is detected that is in the path of the host motor vehicle, the ACC system maintains a driver selected distance (using throttle control and/or limited braking) between the vehicles.
A typical ACC system uses a mechanically scanned radar sensor, which normally improves the ability of the system to detect targets (e.g., other vehicles) in heavy traffic. For example, one commercially available ACC system has a range of one-hundred-fifty meters, an azimuth coverage of fifteen degrees and updates approximately ten times per second. ACC systems generally determine the range of a detected object, as well as the relative speed of the detected object.
It should be appreciated that it is relatively important for an ACC system to accurately determine the range of various in-lane motor vehicles, such as truck trailers. Accurately detecting the range of in-lane motor vehicles is even more desirable in an ACC system that performs stop and go functions. As is well known, a stop and go ACC system provides motor vehicle control down to approximately zero speed, which allows the ACC system to be utilized in urban environments and during various traffic conditions, e.g., during traffic jams. It should also be appreciated that a stop and go ACC system requires operation at very low speeds and, thus, necessitates relatively accurate detection of leading motor vehicles at close range such that safe following and stopping distances can be maintained.
However, at close range, the range to a truck trailer can be difficult to accurately detect due to the configuration of the trailer. That is, truck trailers generally provide multiple radar reflections at close range, e.g., approximately 20 meters and under. Further, the sensor of the ACC system may track an axle of the trailer (instead of the rear of the trailer), as the sensor has a limited vertical field of view at close proximity to the rear of the trailer. A typical range differential between a rear of a truck trailer and a rear axle of the trailer is about 3.5 meters. In stop and go ACC systems, a significant collision risk occurs when a sensor is misreporting the true range by 3.5 meters, which can occur when the sensor reports the range to the rear axle of the trailer instead of the range to a rear of the trailer.
What is needed is a practical technique for an adaptive cruise control (ACC) system that allows the ACC system to safely operate at low speeds by accurately detecting a lead motor vehicle at close range so as to maintain a safe distance between the lead motor vehicle and a trailing motor vehicle in which the ACC system is installed.